Unable to transmit AT commands to a Quectel EC25-AF series modem Windows 10 PC via USB or TCP/IP

IoT Modules LTE Standard Module
1

SOLUTIONS TRIED:

  1. Enabling SSH on the modem and connecting via Putty running on Win10 PC over TCP/IP.
    Result: I’m able to login to SSH as root user but, the modem does not accept AT commands. It does accept other unix commands.

  2. Connecting modem to my Win10 PC via USB serial port without USB device drivers from Quectel.
    Result: Unable to connect to SSH via Putty.

  3. Connecting modem to my Win10 PC via USB serial port AND INSTALLING Quectel_LTE&5G_Windows_USB_Driver_V2.1 device drivers for EC25 modems.
    Result: Modem not recognized in Windows device manager; no connection possible.

  4. Connecting modem to my Win10 PC via USB serial port AND INSTALLING Quectel_Windows_USB_DriverQ_NDIS_V2.3_EN-1 device drivers for EC25 modems.
    Result: Modem recognized in Windows device manager but grayed-out; device manager states “device installation is incomplete - resolve by reconnecting USB device”; despite multiple attempts to reconnect modem to multiple different USB ports - modem does not activate in device manager therefore, no connection is possible.

QUESTIONS:

  1. Are Quectel device drivers required to connect a Windows PC to a Quectel modem using USB? If not, what is?

  2. Have I tried the correct driver versions listed under “Solutions Tried” above? If not, what versions should I be using?

  3. Can AT commands only be transmitted via serial connections and NOT via TCP/IP? If so, how?

Thanks in advance for any assistance you can offer.

OEM Modem: Quectel EC25-AF series Modem
OEM Firmware: Quectel: EC25AFFDR07A09M4G
Supplier Modem: Protectli IDG400-0TE0C
Supplier Firmware: Protectli 00004L0.K21_a21.0000
PC Windows Version: 10.0.19045 Build 19045